exodus3000fandomcom-20200214-history
Yttrium
Yttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanoids and has historically been classified as a rare earth element. Yttrium is almost always found combined with the lanthanoids in rare earth minerals. Its only stable isotope, 89Y, is also its only naturally occurring isotope. In 1787, Carl Axel Arrhenius found a new mineral near Ytterby in Sweden and named it ytterbite, after the village. Johan Gadolin discovered yttrium's oxide in Arrhenius' sample in 1789, and Anders Gustaf Ekeberg named the new oxide yttria. Elemental yttrium was first isolated in 1828 by Friedrich Wöhler. The most important use of yttrium is in making phosphors, such as the red ones used in cathode ray tube displays and in LEDs. Other uses include the production of electrodes, electrolytes, electronic filters, lasers and superconductors; various medical applications; and as traces in various materials to enhance their properties. Yttrium has no known biological role, but exposure to yttrium compounds can cause lung disease in humans. Characteristics Yttrium is a soft, silver-metallic, lustrous and highly crystalline transition metal. As expected by periodic trends, it is less electronegative than its predecessor in the group, scandium, more electronegative than its successor in the group, lanthanum, and less electronegative than the next member of period 5, zirconium. Yttrium is the first d-block element in the fifth period. The pure element is relatively stable in air in bulk form, due to passivation resulting from the formation of a protective oxide (Y2O3) film on its surface. This film can reach a thickness of 10 µm when yttrium is heated to 750 °C in water vapour. When finely divided, however, yttrium is very unstable in air; shavings or turnings of the metal can ignite in air at temperatures exceeding 400 °C. Yttrium nitride (YN) is formed when the metal is heated to 1000 °C in nitrogen. The similarities of yttrium to the lanthanoids are so strong that the element has historically been grouped with them as a rare earth element, and is always found in nature together with them in rare earth minerals. Chemically, yttrium resembles these elements more closely than its neighbour in the periodic table, scandium, and if its physical properties were plotted against atomic number then it would have an apparent number of 64.5 to 67.5, placing it between the lanthanoids gadolinium and erbium. It often also falls in the same range for reaction order, resembling terbium and dysprosium in its chemical reactivity. Yttrium is so close in size to the so-called 'Yttrium group' of heavy lanthanoid ions that in solution, it behaves as if it were one of them. Even though the lanthanoids are one row farther down the periodic table than yttrium, the similarity in atomic radius may be attributed to the lanthanoid contraction. One of the few notable differences between the chemistry of yttrium and that of the lanthanoids is that yttrium is almost exclusively trivalent, whereas about half of the lanthanoids can have valences other than three. Value The base value of each unit of ranges between 9 and 29Ð per unit, with up to 3 units being found at any one time. Presence on Mars: Rare Category:Chemical elements